Pickling Brass

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Pickling Brass

Postby jake_leg » Mon Mar 28, 2011 1:51 pm

Here excerpts from an experimental paper relevant to the subject of corrosion in lead containing brass. Boldface emphasis added. The pickling procedure is slightly different from the well-known procedure recommended by John Palmer in How To Brew (slow pickle in dilute acetic acid rather than fast pickle in acetic/peroxide) but the idea is the same, to take the surface lead into solution as lead acetate. The tests were done over long periods in distilled water but brass corrosion could be expected to be many times quicker in acid and the presence of organic substances, conditions that might pertain in a fermenter or boiling vessel with brass fittings.

CORROSION / Volume 48 / Issue 12 / CORROSION ENGINEERING

Leachability of Lead from Selected Copper-Base Alloys
Corrosion 48, 1040 (1992); doi:10.5006/1.3315907 (7 pages)
J. I. Paige and B. S. Covino, Jr.

Abstract

The Bureau of Mines has conducted research on the selective leaching of lead from copper-base alloys in high-purity water. The alloys in this study were selected as representatives of those used in various plumbing system fixtures such as faucets and valves. Leaching tests were conducted for a total period of 14 days and at temperatures of 25, 50, and 75°C. An acetic acid pretreatment was used in an effort to reduce the amount of lead that was leached from the alloys. The results show that, with the exception of the more complex yellow brasses, more lead is leached into water from alloys containing greater concentrations of lead and that the rate of lead leaching decreases with exposure time. Higher temperatures had relatively little effect on the leaching of lead. Lead was preferentially dissolved from all of the alloy groups. Of the small total amount of alloy dissolved, more Pb, 10 to 59 times, was dissolved than would be predicted from the proportional quantity of Pb present in the alloy (0.1 to 7.0 wt% Pb). Typically, the amount of Pb dissolved in any given test period exceeded the Environmental Protection Agency proposed action limit of 0.015 mg∕L.

...

Effect of Pretreatment

A preliminary study was conducted on alloy C83600 to determine if the smeared Pb film could be successfully removed by a pretreatment procedure. Samples of alloy C83600 were leached in 1.2 N acetic acid for 4 h-, 8 h-, and 24-h periods. Then, the sample surfaces were examined using EDS on the SEM. The examination revealed that approximately 50% of the Pb was removed after 4 h, approximately 75% was removed after 8 h, and it was difficult to find any traces of Pb remaining after 24 h of treatment.
Based on these findings, the second series of tests was conducted in a manner identical to the first series with the exception that all alloys were preleached in 1.2 N acetic acid for 4 h and the only temperature tested was 25C. A comparison of the results for series no. 1 and no. 2 can be seen in Figure 3 and Table 3. This shows that the total amount of lead leached from most of the alloys did not decrease. In fact, the treated model alloys actually showed a substantial increase in the amount of Pb leached from the samples. However, an analysis of the percentage of lead leached during the first 24-h period shows that the pretreatment does have a positive effect. On average, one fourth of the total lead leached in 2 weeks, a reduction over non-pretreated samples, was leached out during the initial 24 h of the exposure period.

Image

[Here are the results graphically] for the semi-red brasses, alloys C83600 and C84400, which are reported to be the most heavily used alloys for production of plumbing fittings in the United States.

Image

...

Conclusion

Pretreatment to remove lead from the surface did not significantly reduce the total amount of lead leached from any alloy during testing.
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Re: Pickling Brass

Postby Bushman » Mon Mar 28, 2011 2:29 pm

Interesting info, I avoid brass so it never becomes an issue but know some people have used the pickling technique.
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Re: Pickling Brass

Postby Husker » Mon Mar 28, 2011 2:36 pm

Can this study be validated? If so, I think we may want to sticky this.

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Re: Pickling Brass

Postby jake_leg » Mon Mar 28, 2011 11:28 pm

There are many patent applications for processes to remove leachable lead from brass and copper alloys. All the ones I have seen involve an acid pickle of some kind, and I am sure that they all succeed in removing surface lead.

To my mind Paige and Corvino throw doubt on the assumption that removing surface lead is sufficient to render the materials safe from future leaching.

Acetic pickling leaches significant quantities of zinc as well as lead (http://www.patentgenius.com/patent/6284053.html). Dezincification exposes more lead which then leaches out (http://www.csass.org/v50n2p97.pdf). Perhaps this mechanism explains part of their findings.

Similar results relating to leachability of different alloys were obtained from this EPA study.
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Re: Pickling Brass

Postby aqua vitae » Tue Mar 29, 2011 3:26 am

Is there any studies on pickling they way recommended on theese boards? The pickling in your study was performed with acetic acid only, and I am sure the hydrogen peroxide is there for a reason.

My alcohol consumption is too small for me to worry about the small amounts of lead in brass (got to be a few gallons a month before the lead becomes a real issue I reckon [please correct me if I'm wrong]). But, brass gives a metallic taste to the spirits unpickled that seems to go away if you pickle it.
It's easy to test this. Soak pickled and unpickled brass in 95.6% for a few days and dilute and taste.
I have not done the test but IIRC riku have done a similar test and reported that the spirit is unaffected by pickled brass.

But if you want to be 100% safe use stainless instead.
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Re: Pickling Brass

Postby jake_leg » Tue Mar 29, 2011 6:09 am

It is best to avoid prolonged contact between brass and anything you consume. Good practice will minimize risk: rinse the still after use, and do not run it so hard that you entrain wash in the vapour. I wouldn't like to quantify the risk because there is no known safe limit for lead exposure. Put it this way, the alcohol is more dangerous.

Mainly peroxide just speeds things up. I don't understand all of the chemistry but here are the basics.

Lead leaches into water by a galvanic reaction (http://www.epa.gov/nrmrl/pubs/625r93001/625r93001.pdf pp 10-12).

Pb -> Pb2+ + 2e-

Electrons are donated to the adjacent brass via the electrolyte. Acetate ions chelate the Pb2+ and render it soluble, exposing further lead metal to the electrolyte. In dilute acetic acid the reaction proceeds slowly. Hydrogen peroxide speeds the process by soaking up electrons.

2H2O2 + 2e- -> 2H2O + O2

Acetic acid will also leach zinc and copper into solution. Adding peroxide will speed up these side reactions too but it may not accelerate all of these reactions equally. You might be taking proportionally more copper into solution. Especially since there is an equilibrium between acetic acid, peroxide, and peracetic acid which is a strong oxidizer.

(As an aside, one of the main ways to prevent lead leaching is to add phosphate salts: Pb3(PO4)2 is extremely insoluble. If your boiler contains brass it might be worth throwing out the lemons and acidifying your brew with phosphoric acid. It used to be one of the ingredients in Coca Cola.)
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Re: Pickling Brass

Postby tafinaf » Wed Mar 30, 2011 12:53 pm

jake_leg wrote:Acetic pickling leaches significant quantities of zinc as well as lead (http://www.patentgenius.com/patent/6284053.html). Dezincification exposes more lead which then leaches out (http://www.csass.org/v50n2p97.pdf).

That does not surprise me. Zinc is among the keenest elements to react with just about anything. It will sacrifice itself to protect other metals (hence sacrificial anode and galvanization). Lead, on the other hand, is among the most inert metals. Sulphuric acid is (or at least used to be) produced in lead containers because it does not attack the lead. And sulphuric acid is one of the strongest acids there is. Any metal other than lead in your car battery would not last an hour.

Question: does anyone know (and I mean, know, not guess) the relative solubility of lead in ethanol vs. water? My gut feeling is that any metal dissolves more readily in water than in ethanol, but I have no hard facts to back it up.
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Re: Pickling Brass

Postby jake_leg » Wed Mar 30, 2011 4:31 pm

Not sure you're 100% correct there. If you leave a lead acid battery discharged the lead cathode will in fact react to form lead sulphate. Charging the battery reverses the reaction.

Lead is more reactive than copper (higher in the galvanic series). That's why lead leaches from brass in preference to copper.

Ethanol is a less polar solvent than water so in general any metal salt will be less soluble in alcohol than in water.

It is certainly possible to dissolve lead in alcohol solution. In ancient times lead acetate was used as a sweetener for wine.
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Re: Pickling Brass

Postby tafinaf » Sun Apr 03, 2011 4:49 pm

I stand corrected on lead reactivity. I should do better than rely on what I remember from school nearly 30 years ago. I was never quite comfortable with it anyway: a metal that withstands the attack of sulphuric acid yet a fresh cut doesn't stay shiny for more than a few seconds? I wonder why lead was the metal of choice for lining chambers for sulphuric acid production, though. But that is straying too far off topic...

Water's polarity is what I had in mind WRT metals' solubility. In other words, the more alcohol the less dissolved metal. That was my gut feeling, but it goes against the common argument on this forum ("water/drink/food safe is not the same as hot alcohol vapour safe"), and I do not have any hard data with measurements like e.g. the brass pickling study.
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Re: Pickling Brass

Postby jake_leg » Tue Apr 05, 2011 10:21 pm

Here's another thing on pickling brass. The waste product will be a toxic brew of lead salts which should not be chucked down the drain but disposed of properly according to local regulations.
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Re: Pickling Brass

Postby sterlingchap » Tue Apr 12, 2011 6:36 am

Is the leaching confined to copper (as acetate) if you hard copper plate the insides of all brass accessories/fittings to "hold the lead away" from potential leaching? Note that hard copper plating brass (vs thin deposition) is not as easy as a casual observer might think!

BTW, in pharmaceutical manufacturing, they use either glass (most acid environments) or stainless steel (most alkaline) for reactor vessels. My understanding is that stills work better when made of copper because copper helps remove sulphur compounds (bad taste, bad smell) from the distillate. At the expense of copper contamination if not properly cleaned first, I suppose.
We shouldn't underestimate the risks in tardy preparation of even a pure copper still. Such as leaving it standing, wet, in CO2-containg air (i.e. carbonic acid available to leach out copper as copper carbonate.) Copper can do you harm too!
If someone could publish how the pro distilleries minimise copper exposure via their cleaning/preparation regimes, it would be valuable insight for us all.
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Re: Pickling Brass

Postby seaguy » Fri Nov 04, 2011 7:29 am

Found this on northernbrewer.com:

Brass and Lead - Should I Pickle or Not.....
OK, some of you may have chimed in on my previous posts on the subject of brass and lead in your brewing. I have had the opportunity to run a pretty conservative experiment to determine the influence of lead, from brass in your brewery setup. The experiment goes as follows:

3 - two gallon batches of tap water were acidified, using phosphoric acid to a pH of 4.0 (conservative for beer). In one batch a 3/8 inch barb/MPT was added and boiled for two hours (covered). A second 3/8 inch barb was pickled using the 2:1 vinegar-peroxide solution and then added to the second kettle and boiled for two hours (covered). The third was my equipment blank. I collected a sample from each pot and had them analyzed for total lead. Here are the lead results:

Blank - Non-Detect
Not Pickled - 6 ug/L
Pickled – 9 ug/L

The MCL for lead is 15 ug/L, and as you can see, by running this conservative experiment we do introduce lead to our beer however we are still under the MCL. Switching out your brass for stainless steel will save you about this much lead, maybe less, but probably not worth the additional cost.

More importantly, the pickling method actually resulted in lead levels higher than those of the non-pickled brass, confirming my previous thought that pickling brass only removes surfacial oxides, it does nothing for the leachability of lead within the brass. In fact the surface oxides may actually inhibit lead leaching! Anyway, the results between the two tests are so close that it really does not matter if you pickle or not, but I certainly will not be taking the time to pickle my brass in the future :lol:!
He went on to say than the PB levels from tap water running through chromed brass fixtures was recorded at 12 ug/L. Might be a good excuse to stop drinking water :lol: .
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Re: Pickling Brass

Postby rad14701 » Fri Nov 04, 2011 1:15 pm

seaguy wrote:Found this on northernbrewer.com:

Brass and Lead - Should I Pickle or Not.....
<<< SNIP>>>

The only issue with those findings is that virtually all beers, even craft beers, are under 10% ABV... Many sugar washes ferment to higher than that... You need to worry more about high temperature high proof alcohol vapor and liquid up to 96.5% ABV reacting with the brass... There's a big difference between beer and distilled spirits...
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Re: Pickling Brass

Postby kartongemi » Mon Nov 14, 2011 7:40 am

hi all
do you use % 100 hydrogen peroxide or hydrogen peroxide solution(which is mix of water and %3 hydrogen peroxide)?
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Re: Pickling Brass

Postby spidermunkeyman » Sat Jun 29, 2013 9:28 am

There is no need to involve brass in the vapor path... you can get copper to slip drain connectors for the sight windows... check out Acklands theyre like 15 bux each or something. Why not just use copper and not have to worry about pickling at all?
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Re: Pickling Brass

Postby cornsqueezer » Sun Jun 30, 2013 9:12 am

Imo I would avoid any materials that were suspect of contaminating my product, so for me it's copper, stainless& teflon for building materials :thumbup:
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Re: Pickling Brass

Postby friendly1uk » Fri Oct 25, 2013 8:40 am

Couldn't you tin them?

eg: Heat them and cover them in plumbing solder. I'm all set to do it, but I can't find anyone talking about it. I thought I would share, to either help or get help
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Re: Pickling Brass

Postby Mountainshine07 » Sat Feb 17, 2018 10:38 am

What about using a brass ball valve as a drain for the pot/thumper?
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Re: Pickling Brass

Postby still_stirrin » Sat Feb 17, 2018 12:58 pm

Mountainshine07 wrote:What about using a brass ball valve as a drain for the pot/thumper?

Is the “ball” actually brass? I bet it’s stainless. But the valve body is probably yellow brass, and if it’s a contemporary valve, it (more than likely) has no lead in the alloy. So, it may be OK to use. But double check the valve stem seals to ensure that they are NOT rubber. Teflon is OK however.
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Re: Pickling Brass

Postby cede » Sat Feb 17, 2018 2:49 pm

New valve should be lead free, unless it's NOS made 20 years ago.

still_stirrin wrote: But double check the valve stem seals to ensure that they are NOT rubber.

+1, well if it is rubber you'll notice it sooner than later, rubber will "burn" is some way !
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